The present invention relates to a switching control system for an electrically adjustable patient chair and in particular to a relay control circuit that utilizes binary switching to control the various motor windings in the chair.
Patient chairs utilized in medical and dental offices typically have electrical height, tilt and/or head adjustment controls. A patient chair with all three adjustment features requires six different motor windings; namely lift up and lift down, tilt back and tilt forward, and head back and head forward. Generally, it has been the practice to provide high current switches that are connected directly in series with the respective motor windings to control the energization thereof. The disadvantages with this approach, of course, are that the control switches must be large and therefore expensive, and high current wiring must be run from the switches to the motors, thus necessitating the use of a rather large cable if a remote switching console pod is utilized.
The obvious approach to avoid these disadvantages is to provide a relay for each motor winding which eliminates the need for having the control switches carry the entire load current. The problem with this approach, however, is that for a chair having six different motor windings, six separate relays are required. The present invention seeks to simplify even further the complexity of the high current wiring for a patient chair of this type by utilizing a reduced number of relays connected in binary fashion to control all of the motor windings. In particular, for a chair having six motor windings, the switching control circuit of the present invention requires only three relays. In this manner, the control circuit is simplified by making more effective use of the high current components in the system.
Additional objects and advantages of the present invention will become apparent from a reading of the detailed description of the preferred embodiment which makes reference to the following set of drawings in which :